比較簡單，直接上程式碼

import UIKit

import WebKit

import SnapKit

class CMWebVC:

UIViewController

    var webUrl: String?

    var webView: WKWebView =WKWebView()

var progressView:UIProgressView = UIProgressView()

    var closeBtn: UIButton!

    override func initVC() {

        webView

webView.navigationDelegate =self

    }

deinit {

        webView.removeObserver(self, forKeyPath:"estimatedProgress")

webView.navigationDelegate =nil

    }

    override func viewDidLoad() {

super.viewDidLoad()

// webview

        view.addSubview(webView)

        webView.snp.makeConstraints { (make)in

            make.width.height.equalToSuperview()

        }

// progressview

view.addSubview(progressView)

        progressView.snp.makeConstraints { (make)in

            make.width.equalToSuperview

            make.height.equalTo(3)

            make.top.equalToSuperview()

        }

progressView.tintColor =UIColor.ColorBgTheme()

progressView.isHidden =true

// load url

        if webUrl !=nil {

            webView.load(URLRequest(url:URL(string: webUrl!)!))

        }

        // shear

        self.showRightItem(image:"nav_share") {

        }

    }

    override func viewWillAppear(_ animated:Bool) {

        super.viewWillAppear(animated)

self.closeButton()

    }

    override func viewWillDisappear(_ animated:Bool) {

self.closeBtn.removeFromSuperview()

    }

    func closeButton() {

        if self.closeBtn ==nil {

            self.closeBtn =UIButton(frame: CGRect(x:44, y: 0, width:44, height: 44))

            self.closeBtn.setTitle("關閉", for: .normal)

            self.closeBtn.setTitleColor(UIColor.black, for: .normal)

            self.closeBtn.addAction({ (button)in

                self.navigationController!.popViewController(animated:true)

            })

self.navigationController?.navigationBar.addSubview(self.closeBtn)

        }

    }

    override func observeValue(forKeyPath keyPath:String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {

        // 載入進度

        if keyPath == "estimatedProgress" {

            let newprogress = change?[.newKey]!as! Float

            let oldprogress = change?[.oldKey]as? Float ??0.0

//不要讓進度條倒著走...有時候goback會出現這種情況

            if newprogress < oldprogress {

                return

            }

            if newprogress == 1 {

                progressView.isHidden =true

                progressView.setProgress(0, animated:false)

            }

            else {

                progressView.isHidden =false

                progressView.setProgress(newprogress, animated:true)

            }

        }

    }

    func webView(_ webView:WKWebView, didFinish navigation: WKNavigation!) {

progressView.isHidden =true

        progressView.setProgress(0, animated:false)

    }

    func webView(_ webView:WKWebView, didFail navigation: WKNavigation!, withError error: Error) {

progressView.isHidden =true

        progressView.setProgress(0, animated:false)

    }

    override func navigateBack() {

        if webView.canGoBack {

            webView.goBack()

        }

        else {

            super.navigateBack()

        }

    }

}